Conventional continuous magnetic storage technology employs a magnetic medium formed on a disk to store information as “bits” across a few hundred magnetic grains formed on a magnetic recording layer of the medium, i.e., the magnetic medium. The bits are recorded by directionally magnetizing ferromagnetic material to represent a binary digit as either a logical 0 or a logical 1. Information is written to, recorded, on the magnetic medium as it rotates past a device called a read-and-write head (abbreviated as the “head” herein). The head operates very close (e.g., tens of nanometers) over the magnetic surface of the medium. The head is used to detect (read) and modify (write) the magnetization of the material of the magnetic medium immediately under it.
It is generally accepted that increases in areal density in conventional magnetic media are achieved primarily by scaling the diameters and the number of magnetic grains per recorded bit, which must be large to maintain an acceptable signal-to-noise ratio (SNR). As magnetic grain sizes are reduced, thermal fluctuations can spontaneously reverse the grain magnetization direction. This limits the areal storage density that can be practically achieved using conventional magnetic storage technology.
Patterned media is a new magnetic storage technology being considered by the disk drive industry to increase the areal storage density of a magnetic medium beyond the one terabit (1e12 bits) per square inch. In patterned media, information is stored in a uniform array of patterned cells, storing one “bit” per cell, rather than storing information across a few hundred magnetic grains allowing for greater areal density than normally possible with conventional magnetic storage technology. The patterned cells are formed of magnetic material on the magnetic medium portion of a storage disk. The magnetic bits are recorded on predefined, single domain patterned cells or islands of magnetization that can be magnetized and demagnetized using the head in much the same way as is currently done in conventional magnetic storage technology. Distinct bit patterns may be created by magnetizing and demagnetizing the patterned cells.
The patterned cells may be formed on the magnetic medium using manufacturing processes different from conventional continuous magnetic media. A magnetic medium with patterned cells formed thereon may be referred to as a patterned medium or bit patterned medium. The patterned cells may be formed on the magnetic media at the time of manufacture. At such time, distinct bit patterns may be formed when the media is formatted to indicate read-head position and track number, otherwise known as servo information. There are presently a variety of methods for generating the patterned cells in patterned media, although it is an area of intense research. One method employs photo-lithography to pattern the underlying magnetic media and form the patterned cells.